Pressure differential servomotor and control



Dec. 5, 1950 G. R. ELLIOTT PRESSURE DIFFERENTIAL sERvoNoToR AND CONTROL 5 Sheets-Sheet 1 Filed Oct Dec. 5, 1950 G. R. ELLIOTT PRESSURE DIFFERENTIAL SERVOMOTOR AND CONTROL v5 sheets-sheet 2 Filed Oct. 3. 1945 .alla filial nvx 34.54555 n m l m Dec. 5, 1950 G. R. ELLIOTT 2,532,801

PRESSURE DIFFERENTIAL sERvoMofroR AND comRoL 3 Sheets-Sheet 3 Filed Oct. 3, 1945 INVENTOR. 60,600 @k /07 Wdh/w TTORIYEY Patented Dec. 5, 1950 PRESSURE DIFFERENTIAL SERVOMOTOR AND CONTROL Gordon R. Elliott, Ferndale, Mich., assignor t Irving A. Puchner and Edward U. Demmer,

Milwaukee, Wis.

Application October 3, 1945, Serial No. 619,947

8 Claims.

This invention relates to servo-motors per se of general utility of the type disclosed in applicants pending applications Serial No. 508,033, filed Oct. 28, 1943, now Patent Number 2,440,654; Serial No. 573,997 filed January 22, 1945, now Patent Number 2,455,984; and .Serial No. 593,723 filed May 14, 1945, now Patent Number 2,455,985, all three of which the present application is a continuation-in-part.

More particularly, the invention relates to a servo-motor having a chamber containing a movable member responsive to pressure differentials in said chamber on Aopposite sides thereof, with a power transmitting movable means joined to said movable member, together with a valve means for controlling said pressure differentials.

It is the object of this invention to provide a servo-motor consisting of a chamber, a diaphragm sealed therein and movable in response to a pressure differential on opposite sides there-v of, a motion transmitting means joined at one end to said diaphragm, and a valve means for regulating said pressure diiferential.

vIt is the further object to provide a power chamber in conjunction with a hydraulic cylinder adapted to deliver fluid under pressure, together with a movable diaphragm'in said chamber, a piston in` said cylinder, means joined to said diaphragm adapted for effecting movement of said piston, and an air and vacuum control valve intermediate said chamber and cylinder for governing movement of said diaphragm.

These and other objects will be seen from the following specification, claims and drawings, in which preferable operative embodiments of the invention are illustrated. In the drawings:

Fig. l is a side elevational section of a servomotor including a diagrammatic indication of a vehicle master cylinder, intake manifold, wheel brake cylinders, and conduits therefor.

Fig. 2 is a different embodiment of the same.

Fig. 3 is a still different embodiment of the same.

Fig. 4 is an enlarged fragmentary section of the valve and hydraulic piston shown in Fig. 1.

It will be understood that the servo-motors in the drawings illustrate merely one operative use thereof by way of example, and that other embodiments and uses thereof are contemplated within the scope of the claims hereinafter set out. In Fig. l, the vehicle brake wheel cylinders i l are joined by conduit I2 to outlet port I3 in the end of hydraulic cylinder I4. Master cylinder I5 with manually operable foot pedal actuated means I6 is joined to-uid intake port Il of cylinder I4 by conduit I8.

The power chamber consisting of hollow circular opposing shell members I9 and 2li is joined to the left end of hydraulic cylinder I4 with the air land vacuum valve consisting of valve body members 2l and 22, interposed therebetween.,

The vehicle intake manifold 23 provides a vacuum source to vacuum port 24 in valve 2I-22 by interconnecting conduit 25 with check valve 26 interposed. On the other hand, air lter 21 is joined to the valve air intake port 28 by conduit 29'.

Valve body 22 is secured tomember 29, forming an integral part of cylinder I4, by a plurality of circularly arranged studs 30, two of which are shown in the drawing.r The complementary Valve body 2i is likewise secured to valve body 22 by a plurality of similar circularlyarranged bolts, not shown in the drawing, with the central end portion of shell 20 being interposed therebetween to provide a valve air seat plate 3l with air inlet openings 32.

Fluid control piston 33 with sealing cupY 34 is movable within cylinder i4 being secured to one end of the hollow power rod 35 by the two pins 36 retained by coil spring 31. Hollow Valve control piston with sealing cup 39 is slidably provisioned within cylinder I4 in spaced relation to fluid control piston 33. y

Power rod 35 slidably supported through valve piston 3B is also slidably journaled through thel elongated hollow portion 4I! forming a part of valve body 2l, with a suitable seal 4I being pro' visioned within the end of member Y4E? between member 40 and said rod.

Concave annular flexible diaphragm 42 with outer annular sealing rib 43, reinforced by hollow annular plate 44 is secured centrally to the left end of hollow power rod 35 by threaded nuts 45 on opposite sides thereof. Circular spring retainer plate 4E registers with reinforcing plate 44, with coil spring 41 being interposedY between I plate 46 and valve body 2l, to normally and resiliently retain diaphragm 42 in the inoperative position shown.

The opposing shell members I9 and 20 are respectively annularly flanged at 48 and 49 for encompassing the edges of annular rib 43 whichv forms a part of diaphragm 42. Annular concave broken clamp ring 50 is positioned over shaped flanges 48 and 49 the edges of said flanges resting in the bent portions 5I and 52 respectively ofclamping ring 50.

Referring again to Fig. l, coiled spring 5l is provisioned within valve body 2I-22 with its left end engaging the valve housing and with its other end registering with valve control piston 38 to normally resist movement thereof to maintain, when inoperative, vacuum communication between vacuum chamber 58 and chamber 59. Vacuum communication is established with chamber SI1 in shell i9 by means of openings 6I in hollow rod 35.

Vacuum is constantly maintained in chamber' 52 within shell member 29 by means of passage 63 in valve body 2I-22 which is joined by vacuum conduit 25. With vacuum communication established in both chambersv 6B- andA 32 it is seen that there is an equilibrium of pressure on opposite sides of diaphragm 42. By the existence of spring 41 it is thus seen thatk when inopera-Y tive, the diaphragm and the power shaft assume the position shown in Fig. 1.

To obtain power braking, valve piston 3B is projected to the left on application of master cylinder I5. Piston 38 engages diaphragm; plate 34 carried by flexible diaphragm 65- peripherally retained: between valve body membersand 22. A secondary diaphragm plate4 G3 of reduced diameter is securedon the opposite side of diaphragm E5 by rivet 61 which extends through both plates and said diaphragm- Rivets El extend outwardly through: air openingsA 32 inair valve seat 3l and are secured at their ends: to air val-ve disc' 68, which is normally seated relative toair valve seat 3I' by coiled spring 69.

Piston 38- when movedv to the left contacts diaphragm plates 64- and- 63- closingoif vacuum communication between vacuum chamber 58 andchamber 53. Further movement tov the left of piston 38- eftects translationto the left of diaphragm S5- and corresponding unseating movement of air valve disc 68 permitting. air in chamber I3 to pass throughE openings 32A in valve seat 3If, and into chamber 53 which is in communica-- tion at all times with ppwer chamber' 6G.

With air in chamber 63 and vacuum maintained in chamber B2', the pressure differential on opposite sides of diaphragm 4:2 eects translation thereof forcefull-v to the right carrying therewith power shaft -fvvhieh.y isfioined tn'bra'keY operating piston 33 to obtainpower braking.

Hydraulic piston 33 has a passage 'Hy therethroughl adapted tovv be closed by ball valve 'il retainedy within piston' 33 byfsnring- 73 and nin M Ball` valve operatingr member adapted to'` unseat ball 1-2 and. to permit. its seating relative to piston passage 'Hc is adiustably retained within the end of hollow shaft 35 by transverse: pin 'It Within slot TI formed therein.

Pin 'l5 a'soadiustabl-y retains flanged sleeve' member 73 relatively toY shaft 35, the ends of pin 'I'B being held7 by coiled spring i9 nrovisioned' between the end flangesl of' said' sleeve. Ring 8@ is interposed between sleeve T8 and sealing cup 39 and is maintained against the latter for movement therewith by the resilient action of spring '13.

Transverse stud 8l extending into cylinder` i4 acts as a stop limiting movement of ring 83 to the right, and' movements of sleeve 'I8 to the left.

Operation O11 initial applicationV of." the vehicle foot pedal' energizing master cylinder I5 and. directing iiuid under pressure through conduit I'8 fluid enters the chamber between pistons 33 and. 33-y effecting movement to the left of valve piston 38 with some uid passing through passage 'H in piston 33.

Ring 83 and sleeve 'I8 follow piston 38 to the left under action of ball spring 13, permitting movement to the left of pin i6 and valve member l5 retained thereby. Ball T2 is thus permitted to close passage Il under expansive action of Spring 73. Movement of sleeve 13 to the left ends when spring 73 becomes inoperative on ball 12" seating over opening 'Il and piston 33; and a spaced relation now exists between Said sleeve and. piston 33.

Movement of piston 38 to the left has operated the air and vacuum control valve 2I-22 and power rod is projected to the right through piston 38 in the manner above described. Piston 33 with. its passage il now closed, operatively acts upon the brake fluid within cylinder I4 directing the same at relatively high pressure to the vehicle brake wheel cylinders iI through port- I3.

Movement of power rod 35 to the right also effects movement of sleeve i8 which is loosely joined thereto by pinV 16. piston 33 move as a unit sleeve member merely floats along therewith but a spaced relation is still maintained between said sleeve and piston 33.

On brake release iiuid pressure the chamber between pistons 33 and 33' is reduced practically to zero permitting return movement of valve piston- 38. to the right under action of spring 51 closingoi the air tochamber and again establishing vacuum communication thereto by return of diaphragm to its initial position and air va-lve disc 33 to its seated'position under actionof spring 5S..

Movement tothe right of piston 38- is accompanied by a relative movement therethroughr to the left of power shaft 35 under action of spring 47.-, and the relatively high fluid pressure in the hydraulic chamber of cylinderi I4. Return oV piston 33 joined to rod 35y is. limited by engage-v ment of sleeve 18 with stop pin 8-I. However it is to be noted that the pre-existing spaced rela-- tion between sleeve 78 and piston 33- permits movement of piston 33- relative to'said Sleeve, and pin 'I6 now retained by sleeve is prevents movemen-t of ball unseating member'15 with the result that ball 12 is promptly unseated permitting a quick release of the? fluid. under pressure in the hydraulic chamber of cylinder i4.

Thus a promptr and quick bra-ke release is obtained immediately upon releaseV of the vehicle foot pedal operating pivotal member I3 which controls the master cylinder; Valvev operating piston 3S returns to the right, pistonV 33 and 35 return to the left, and the ball valve 'l2' is simultaneously unseated releasing uid pressurefrom the vehicle brake cylinders II.

It will be noted that annular ring 82 secured upon power rodA 35 is adapted to engagev coil spring 83 which is housed within the extended portion 43 of valvebody member'Z If, thereby providing a yielding seat for said power shaft.

It will be noted however that spring 83" eiTects a slight translation to the right oi' rod 35 and its piston 33, so` that a spacedy relation is aga-in establishedbetween sleeve' 1:8 and stop pin 8|. Thusv it is seen that on the'next brake'applicati'on sleeve 78 is free to move to the left as above de-` scribed in detail.v

As previously described return movement of piston 33 as well as means 35, 42 under action l of. spring 4l, is limited by engagement orv sleevey However as rod 35 and4 '178 18 with stop pin 8|. However, it will be seen that large spring 41 is now fully expanded. At the same time smaller coil spring 93 has been fully compressed to the extent that there is a small movement to the right of shaft 35 after its brake release return movement.

It is this slight movement to the right of shaft 35 which reestablishes a spaced relation between stop pin 8| and sleeve 18. This initial spaced relation between members 8| and 18 is necessary because it provides a means of permitting seating of ball Valve 'I2 prior to power movement of shaft 35. Consequently shaft 35 is immediately eiTective on actuating piston 33 as ball valve 12 has been seated over opening 1| prior to movement of power shaft 35. Thus any possible lag in brake application is eliminated.

On brake release means 33, 35 and 42 are returning to the left, and means 18 first contacts stop 8|. However, as above described there is still a spaced relation between means 18 and piston 33. And it is the further movement of piston 33 towards the stopped means 18 which has the effect of unseating ball valve 12 for obtaining a very prompt brake release.

It will be understood that with the brakes applied, movement to the right of piston 33 has very little or no effect on the initial leftward movement of piston 38. This follows because even though the brake may be applied, the ilow of pressure fluid from unit I5 does not entirely cease and additional iluid will flow into the chamber between pistons 38 and 33 to-take up the increased volume of that chamber. This follows because any decrease in the fluid pressure in said chamber between pistons 38 and 33 is automatically taken up by the reaction pressure i or pedal feel of the operator in making the master cylinder pedal fully effective.

Referring to the operation of diaphragm means 65 initially, and before brake application, a balanced vacuum condition exists on both sides thereof. However, as piston 38 moves to the left vacuum is cut oil to the chamber to the left of said diaphragm. Further movement to the left of piston 38 unseats air disc 68 so that now there is air to the left of diaphragm 65 with vacuum to the right thereof in chamber 58.

This pressure differential acts on diaphragm 65 tending to move it to the right against the leftward movement of piston 38. Thus it is seen that the pressure differential on opposite sides of diaphragm 65 tends to resist brake application, and the extent of this resistance is proportional to the extent of the pressure differential. Consequently, on brake application a counterforce is created which tends to resist brake application. and which gives to the operator a certain pedal feel as the brakes are applied.

It will also be noted that the inner circular portion of air valve seat 3| is secured at a plurality of points around valve body member 2| by screws 34. It will further be noted that hollow power shaft has a plug 85 at one end for closing off the opening in said shaft from the chamber between pistons 33 and 38.

Referring tov Fig. 2 the vehicle Abrake hydraulic cylinder I4 has an outlet port ||8 for communication with hydraulic brake lines I2 shown in Fig. 2.

In take port I I9 connects with conduit I8 from the hydraulic master cylinder I 5 whereby manually operated brake fluid is supplied under pressure to hydraulic cylinder I4 to be directed through the longitudinal opening |20 within Vpiston |2| slidingly positioned in cylinder I4.

Piston expansion cup |22 carried by piston |2I provides an elective hydraulic seal within cylinder I4.

Power chamber ||0 is positioned at one side thereof with a vacuum inlet connection |23 adapted for connection to vacuum conduit 25 from the vehicle intake manifold 23 in the manner illustrated in Fig. 1.

The vacuum valve body housing |24 extending within power chamber housing ||0 is suitably secured to the annular flange |25 of cylinder housing I4 by bolts |26 and nuts |21. It will be noted that said ilanged portion |25 also forms a part of air and vacuum valve body |24. Power chamber I I0 is likewise retained in xed relation to valve body |24 by bolts |26 as shown in Fig. 2.

A hollow air control diaphragm |28 is peripherally retained between the annularly flanged members |24 and |25 which form the control valve body. Hollow diaphragm stiffening plate |29 is secured on one side of said diaphragm by rivets |30, the other ends of said rivets retaining air valve control disc |3| on the other side of said diaphragm.

Disc |3| is punched outwardly to form the annular flanged member |32 which is adapted to unseat air control disc |33, the latter being normally retained by spring |34 over annular air opening |35 in air valve seat |36. It will be noted that annular air valve seat |36 is peripherally secured between valve body ange |24 and diaphragm |28.

Hollow flanged valve control piston |31 is reciprocably and slidably positioned within the end of hydraulic cylinder i4 in engagement with spring |38, the other end of which is seated against the interior of valve body |24. Piston |31 is suitably sealed from control chamber |39 by the rubber expansion cup |40.

As shown in Fig. 2, vacuum communication established at connection |23 of the power chamber ||0 constantly maintains a vacuum condition in chamber |4| as well as in chamber |42 joined thereto by passage |43 formed within valve body |24-425.

As shown in Fig. 2, vacuum is estabilshed in chamber |44 through openings |45 in hollow power rod |46. It will be noted that movement to the left of valve control piston |31 causes disc |41 thereon to sealingly engage plate |29 cutting off further vacuum communication to chamber 44.

Initially, with vacuum in chambers |4| and |44 power diaphragm |48 peripherally secured within power chamber III), assumes the position shown, with return spring |49 being interposed between valve body |24 and diaphragm supporting plate |50. It will be noted that a suitable seal |48 is provided around rod 46 and within the end of valve housing 24 Fig. 2.

Said diaphragm and plate are centrally secured to hollow power rod |46 by the opposing nuts |5| and |52 threaded on said rod.

Referring to the control valve body |24 it is seen that air is at all times maintained in chamber |53 through air passage |54 formed within valve body members |24 and |25.

As valve control piston |31 moves to the left relatively to rod |45, in the manner hereafter described, it first engages diaphragm disc |29 for cutting off further vacuum communication between chamber |42 and chamber |44. Further movement to the left of piston |31 causes translation to the left of diaphragm |28 as well as the anged member |32 `for unseating spring retaineddisc 133 from its seat |36.

Air in chamber |53 is now able to flow through opening |35 in seat |35, through openings H35 in hollow rod 146 for communication with chamber |44 in power chamber housing |10. Air in chamber |44 and vacuum in chamber 1M disturbs the pre-existing equilibrium creating a substantial pressure diiierential on opposite sides of diaphragm "M8, with the result that said diaphragm is projected forcefully to the right at the same time forcefully projecting power rod '|45 centrally joined thereto. Movement to the 4right of rod lit effects corresponding movement of hydraulic piston |2i in hydraulic cylinder Ill until opening i2@ in piston 12! is closed by engagement of valve member |55 resiliently supported by coil spring its, the outer end of which is adjustably secured by removable cover 57 threaded in the end of hydraulic cylinder 14.

It will be noted that rod 45 is secured at all times to piston i by means of the spring retained ball lock its so that piston 21 always kmoves with rod Ball lock |58 may be manually disengaged from piston |21 in the event it is desired to separate said piston and rod for disassembly and, or cleaning. A plug |59 is tightly secured within hollow rod |45 with a suitable passage formed therein to coincide with and form apart of passage 120 in piston 12|. Ball chain |55 interconnects valve |55 and cover 15? to limit movement of said valve.

Referring to Fig. 2, for conventional operation of the brakes the master cylinder 15 is operated by foot pedal 5 for directing fluid under pressure through conduit 18, into port H9 of the hydrauiic cylinder, chamber 939 and through passage I2@ into chamber lr6@ whence it is directed out connection H8 through conduits i2 to the brake cylinders 1| for the vehicle Vwheels respectively. This initial actuation vof brake pedal 1t will resuit in a partial braking eect upon wheel drums and will also take up the slack of fluid in chamber llil as well as in conduits i2.

As soon, however, as said slack is taken up it will be seen that continued and further actuation of brake pedal I6 will tend to compress fluid within chamber |39 as well as in chamber i653 with the result that valve control piston i3? is projected to the left. In the first instance, it wil1 be seen that disc itil carried by said piston will engage the diaphragm disc |29 for closing olf further vacuum communication to chamber |45 forming apart of power chamber |10. It will be noted that momentarily there is a balanced condition between chambers 4| and |44 with vacuum in both chambers. However, further movement of control piston 13'! to the left effects movement to the left of diaphragm |28 as well as the anged member |32 which unseats spring retained air control disc |33.

Air which is constantly in chamber |53 is thus free to rush through opening 35 in Valve seat |36 for communication with chamber |415 through hollow rod |45. Instantly there is a forceful translation of diaphragm |48 to the right due to the pressure diierential between chambers |41 and 1451 which is proportionate to the surface area of said diaphragm, and which results in forceful translation of power rod |46. Hydraulic piston |21 being joined thereto is also translated forcefully to the right, rst sealing off passage I2@ by engagement of valve member |55. Further movement of hydraulic piston 12| tends to exert a compressive force upon the s, uid in chamber y16|] with the result that va secondary power braking is effected through lines 12. It will be understood that as soon as passage 12] is closed off by engagement with valve member |55, fluid under pressure, which is maintained by continued application of brake pedal |6, 'is directed to chamber |39; and kinasmuch as passage |29 is now closed, it will be seen .that a degree of fluid pressure exists for cooperative action upon the end of piston 12| working in unison with the power rod |46 which is -also eiecting a pressure movement on piston |25 relative to the hydraulic fluid in chamber It.

For example, while the initial braking pressure may be approximately 200 pounds per square inch, power chamber 11@ eiiects a substantial multiplication of braking pressure so that approximately 800 to 1000 pounds per square inch pressure is available. It is understood that the above pressures are given merely by way of illustration and naturally would be varied depending upon the size of power chamber 11S and the surface area of diaphragm it.

Movement Yof piston |2| to the right 'increasing the volume of chamber |39 partially reduces the existing fluid pressure therein permitting a partial return of valve piston l'i to the right under action of coiled spring |33. Diaphragm |28 and plate 12% under action of spring i3d, follow valve piston i3? to the right, permitting air disc |33 to seat itself under action of said vspring |34, cutting oi further airV communication between chambers 153 and 145i. lSaid valve assemblyis now in a balanced condition with further air and vacuum communication to chamber Y| 44 effectively cut oiT.

Brake release is effected by relieving the manual pressure from master cylinder 'i5 with the result that the pressure in chamber |3 is reduced permitting `control piston |31 to return to its initial position under action of `coil spring 138. As soon as control piston is? reaches the position shown in Fig. 2, vacuum communication is again established between chamber Ilil and chamber |44, with the result that an equilibrium in pressure is established on opposite sides of diaphragm M8. Said diaphragm then returns to its initial position 'shown in Fig. 2, under action of coil spring H29. it will be noted 'that return of diaphragm |48 to its initial 'position also effects a corresponding return of power rod |46 as well as hydraulic Vpiston 12| secured thereto.

A stop member i5! is threaded through hydraulic cylinder |13 and projects into chamber 139 to provide a limitation on the return movement of piston |21 as well as power rod lffi and diaphragm |43 secured thereto. The return of piston 12| to its initial position results in the unseating of valve member |55 again opening passage 12d in said piston which communicates with chamber |39. Thus all operating members are again in their initial positions ready for the next actuation ofthe brakes.

It will be understood lthat in the event of a failure of the power braking system or the air and vacuum lcontrol valve therein, manual application of the brakes is still available as above described.

After application of the power brakes, and on release of foot pedal |15, the fluid pressure in control chamber 139 is reduced approaching zero, permitting valve control piston |31 to gradually return to the right, relatively to power rod |46, until it reaches its initial position shown A9 in Fig. 2. At the same time, with high pressure in chamber |60 and opening |20 still closed, piston IZI starts moving back to the initial position shown in Fig, 2 due to the differential of pressure on opposite sides thereof.

The return movement of piston |2I is limited by the return movement of power rod |46 and diaphragm |43 to which it is joined.` As a short period of time elapses before full Vacuum is again established in chamber |44 diaphragm |48 tends to lag in returning to its inoperative position, as shown in Fig. 2, even though under expansive action of spring |49. This lag would be transmitted to piston |2| delaying its return for effecting complete brake release.

However, it is seen by the initial pressure differential between chambers |39 and |69 that, on release of pedal I6, piston I2| is assisted in its return. Furthermore, ball chain |55 limits the return movement of valve |55 guaranteeing the quick opening of passage |20 of piston I2I. Opening of passage |20 immediately effects complete brake release with fluid under pressure in chamber |60 free to escape. Thus brake release is prompt which is a great advantage over power brakes of different construction wherein means are not provided for assisting in the brake release function.

Power chamber IIO is advantageously secured or formed integrally with control valve I24-I25 to provide a compact unit which may be positioned anywhere on the vehicle or truck frame. However, it is contemplated that said power chamber could be remote from the control valve with a suitable linkageinterconnecting the diaphragm and the valve actuating power rod |46.

On the other hand it is also contemplated that valve actuating rod |46 could be forcefully actuated by any other suitable power source acting through a suitable linkage.

It will be understood that while` the power chamber IIO is shown in Fig. 2 with a flexible movable diaphragm therein, it is contemplated that said power chamber could be constructed with a reciprocable piston therein. Creation of pressure differentials on opposite sides of the piston would be eiected exactly as described with respect to Fig. 2.

Referring to Fig. 3 the vehicle brake hydraulic cylinder I4 has an outlet port ||8 for communication with hydraulic brake lines I2 shown in Fig. 1.

Intake port II9 connects with conduit I8 from the hydraulic master cylinder I whereby manually operated brake uid is supplied under pressure to hydraulic cylinder through the longitudinal opening 220 within piston 22| slidingly provisioned in cylinder I4. Piston expansion cups 222 carried by piston 22| at opposite ends thereof provide an .effective hydraulic seal within cylinder I4.

Hydraulic cylinder I4 is provisioned at one end with a vacuum inlet connection 223 adapted for connection to vacuum conduit 25 from the vehicle intake manifold 23 in the manner illustrated in Fig. l.

The vacuum valve body housing 224 extending within power chamber housing 2|0 is suitably secured to the annular flange 225 of cylinder housing I4 by bolts 22|:` and nuts 22'I, with the air filter spacer 223 interposed therebetween. Said filter spacer 228 is transversely slotted for housing air filters 229 through which air is conducted from air inlet 2|4 and baiile 2|4 shown best in Fig. 1.

I4 to be directedA It will be noted that power chamber 2|0 is retained between valve housing 224 and filter spacer 228; and further that diaphragm plate 230 is provisioned within housing 224 and filter spacer 228,

Hollow diaphragm 23| retained at its outer peripheral edge between power chamber 2I0 and valve housing 224 is centrally secured to the annularly flanged portion of plate 230 and movable therewith, Thus chambers 232 and 233 are provided upon opposite sides thereof, with chamber 232 bounded by diaphragm 23| and housing 244, and with chamber 233 bounded by said diaphragm and the annular flanged member 234 forming a part of filter spacer 228 and projecting angularly inwardly with respect thereto.

Chambers 235 and 235 are also provided on opposite sides of the hollow secondary diaphragm 23'? which is peripherally retained between lter spacer 228 and cylinder housing I4 and centrally retained by diaphragm plate 230. Diaphragm plate 230 is of the Aspool type construction, one end of which being secured to diaphragm 23| and the other end of same to diaphragm 231. Central radial openings 230 are provided in plate 230 between said diaphragms providing connection between chamber 235 and chamber 252.

- Hollow secondary piston 238 with suitable piston cup 239 is reciprocably movable within cylinder housing I4 with its annular flanged portion 243 projecting Within chamber 236 above described.

Hollow housing 224 with chambered recess 252, has longitudinally and reciprocably provisioned therein plunger 24| which projects through housing 224 and into power chamber 2I0 at one end, with its other end being slidably disposed through hollow piston 23S, but with its rounded end portion 242 adapted to operatively register with opening 220 in piston 22| for closing off the same from chamber 243. The end portion 242 of plunger 24| is also adapted to operatively engage piston 22| for causing longitudinal translation thereof for exerting pressure upon the brake fluid contained within chamber 244 in power cylinder I4.

It will be noted that a return spring 245 is provisioned within chamber 244 of cylinder I4 between the outer end thereof and the reciprocable piston 22 I Also an expansion spring 24S is interposed between piston 22| and piston 238 for maintaining a variable spaced relation therebetween, and also for holding seal 239 in position relative to piston 233. Also another return spring 247 is provisioned within valve housing 224 interposed between one end thereof and the end of piston 238. It will be noted that av suitable pneumatic seal 248 is provisioned around plunger 24| and within the end of housing 224 for maintaining a suitable seal between the plunger 24| and said housing.

Plunger 24| has a central longitudinal opening 249 in one end thereof which terminates in transverse opening 253 within plunger 24| providing pneumatic communication between chamber 25| within power chamber 2li! and chamber 252 within valve housing 224.

It is seen in Fig. 3 that chamber 252 is adapted for communication with chambers 232, 235 and 236; and also with chamber 233 whenv diaphragm plate 230 is moved to the left relative to the annular flange 234 on spacer 223. It is further seen that vacuum communication to inlet connection 223 is established to chamber 233; and also to chamber 253 through conduit 254 formed within housing members i4 and 222?, and lter spacer 228.

Flexible cup shaped diaphragm 255 peripherally retained by and between the two opposed power chamber housing members 2|3 is adapted to flexing movement within chambers 25| and 253 on opposite sides thereof within power chamber 2MB.

Diaphragm plate 255 substantially circular in shape, registering with the central inner surface ofv diaphragm 255, is provisioned upon the end of the re-ciprocable plunger 25| and secured thereon by the nuts 252i threaded upon opposite sides thereof on plunger 24|. Consequently longitudinal movement of diaphragm 255 within powerl chamber 242, upon the establishment of a pressure differential between chambers 253 and 25|, will cause a corresponding*longitudinal forceful` movement of plunger 247| within valve housing 22!!VV and cylinder I4.

Operation In operation, manual application of the vehicle foot pedal l5 shown in Fig. 1, joining the master. hydraulic cylinder |5 will supply brake fluid under pressure through conduit I8 and port H5 to the hydraulic cylinder i4. Fluid. underpressure thus enters chamber 243. between pistons 22 and 238-and is retained: therein until sufv fcient pressure is developed to cause partial longitudinal movement of piston 22| to the right relative to plunger 24| and against spring 245, uncovering channel 220 therein.

Fluid under pressure thus enters chamber 244 andis-directed out port l i3 and through conduits |72` forinitial normal vehicle brake application. Before brakev application vacuum communica-u tion-from the` engine manifold 23, Fig. 3, has` been established within chamber 253 through conduit 25, connection 223 and conduit 254. Likewise vacuum communication in chamber 25| was also obtained from connection 223, chamber 238,

chamber252, opening 250 and conduit 249, wherepressure in chamber 243 also causes movement to theleft ofA piston 238 within cylinder housing |42` and with respect to plunger 24|. Piston or` vacuum valve 238 engages diaphragm or-vacuum valve. seat 23"|V and its retaining plate 230-closingotf further vacuum communication between chambers 236 and 252, and consequently from diaphragm chamber 25| within power chamber housing 2 I0.

Further movement to the left of piston 238.

causes further translation to the left of diaphragm supporting plate 238 and thediaphragm 23| also joined thereto. This movementA establishes communication between chambers 233 and 235- supplying air from air inlet 2|4 into valve chamber 252, whence it rapidly enters chamber 25| through opening 258 and conduit 249 in valve plunger 24|.

This secondary movement of diaphragm plate 230 against the action of coiled spring 258 and up to the annular boss 224 in housing 224 is facilitated by the pressure diierential between chambers 232 and 235, with vacuum initially in chamber 232 and with air now in chamber 235.

Thus boss 224 denitely limits the movement to the left of piston 238.

At this point a very substantial pressurediferential has been eiected between chambers 253 and 25|, inasmuchas chamber` 253-is in constant communication with the vacuum source, while air communication has been established with chamber 25|. Consequently-diaphragm 255, plate 25B and plungerY 24| are forcefully projected to the right, opposite to the direction ofv movement or piston 238.

The end portion 242 of plunger 24| closingo` conduit 2'20in piston 22| operatively lengagesthe end ofVVA said piston causing longitudinal movement-to the-rightlthereof greatly increasing the uid pressure with-in chamber 244- which is directed-A outthrough port |-|8 and-*throughY conduits I2 to the vehicle brakes. In this'. manner supplemental power braking of' the vehicleis effected.

Movementof piston 22|A to the-.right increasingthe volume of chamber 243, necessarily-reduces the existing uid pressure therein, with the result-,that piston 238 ca-n now, under action of returnn spring 241, return tothe rightholding the valve in balance? that is; holdingvacuum valve-231 closedandclosingair valve 23| for partial or controlled bra-king;`- or on furtherV movement of piston 238 on brakerelease again establishing vacuum communication between chambers 236 and 252 and between chamber 252Y andv chamber 235,; al-so permitting vacuumto be built up again within-` chamber 25| It will be, understood as an equilibrium is again established between chambers 25g| and 253 that plunger 24| andv diaphragm Z55-'joinedl thereto will return to the left4 to its initial position for terminating or releasing the power brake action.

With vacuum in chamber, 2 36` and air in ycl-iamber 235thepressure diierentiaton vacuum valve diaphragm 231 facilitateslongitudinal movement` of diaphragm plate-230 togthe ri'ght; Air valve` diaphragm 23 i, also moving withdiaphragm plate 23.8I engagesI air valve seat 2343i. e. the annular flange 234 forming a partofj member 228thus closing oirv further air communicationbetween chambers 233V and 235:

Flange 234 on spacer 228" also stops. movementment to the right of diaphragm supporting plate.

23.0.18 feeiiteied by the aerien, ef the initially Compressed spring. 258-1 The alfiere pressure dii-- fereniial in. Chambers 235 and; 231i.v` en diaphragm, 2311 also reacts upon piston 233 ,rra variable degree in addiiiente the mereer. less. Steady or` nenvariable pressure exerted by spring` 24]'. This pressure., differential will. be irl. Ap..r.er. rtien. te. the, pressure differential.' en diaphragm. V2 5,5in.1:11am.- bers 25|'and` 253.

Thus a resistance, pressure.. is. created ,in .ehamber 243. ege-.inst the r,r1a1,111a1.1y.created;pressureL frompthe master cylinderY conduit. Igwhichis, irensieriedto feet pedal |6;ir.1 ..rronerien to. the amount of braking pressure exerted. byA dia,- phragm 25,5, thus establishing arelatiopshipbetween amount-o frbraking and" pedallfeeh Piston 238, is now in its initiali position as shown in Fig, 3, andl with plunger 24|* returned to its-initial position, piston 221|- underaction of'- coiled spring 244- is also permitted-to return to itsv initial brake release position. It'is noted that* the outer portion of: pistonflange- 240- provides reinforcement for the flexing-movement-of-fthe*Y vacuum valve diaphragm 231.

The above construction particularly specified in Fig. 3 provides effective power braking to supplement the normal vehicle manually'operated hydraulic brakes. Said structure provides for an air operated diaphragm within a power chamber for obtaining a power` stroke upon the piston within the brake operating hydraulic cylinder.

It is seen that the power stroke is effected by longitudinal movement of plunger 24! operatively and directly engaging the co-aXial piston 22H within the hydraulic brake operating cylinder. The particular construction shown is compact in its arrangement inasmuch as the power plunger 24| slidably operates within and through the air and vacuum control valve housing.

It is further to be noted that the vacuum valve operating control piston is reciprocably movable within said control valve housing and also within the hydraulic brake cylinder. Furthermore power plunger 24| is centrally and slidably disposed through control piston 23%, with its movement being entirely independent of the movement of said control piston. In fact on power brake application, movements of the plunger and the valve piston are in opposite directions.

Having described my invention, reference sho-uld now be had to the claims which follow for determining the scope thereof.

I claim:

l. The combination, an air and vacuum valve housing, a power chamber joined thereto, a movable member within said power chamber defining operating and vacuum chambers on opposite sides thereof, a vacuum source joining said housing and conducted therethrough to said vacuum chamber, air inlet ports in said housing, a plunger rod secured to said movable member and slidably disposed through said valve housing, said rod having a partial longitudinal passage terminating in said operating chamber and within said housing, and movable means in said housing for alternately providing air and vacuum communication to said operating chamber.

2. The combination, an air and vacuum valve housing, a power chamber joined thereto, a movable member within said power chamber defining operating and vacuum chambers on opposite sides thereof, a vacuum source joining said housing and conducted therethrough to said vacuum chamber, air inlet ports in said housing, movable means secured to said movable member and slidably disposed through said/valve housing, said movable means having a partial longitudinal passage terminating in said operating chamber and within said housing, movable valve means in said housing for alternately providing air and vacuum communication to said operating chamber, and manually actuated means engageable with the movable valve means in said valve housing.

3. The combination, an air and vacuum valve housing, a power chamber joined thereto, a movable member within said power chamber defining operating and vacuum chambers on opposite sides thereof, a vacuum source joining said housing and conducted therethrough to said vacuum chamber, air inlet ports in said housing, movable means secured to said movable member and slidably disposed through said valve housing, said movable means having a partial longitudinal passage terminating in said operating chamber and within said housing, movable valve means in said housing for alternately providing air and vacuum communication to said operating chamber, a hydraulic cylinder joined to said housing, and a 4. in combination, an air and vacuum valve housing, a power chamber joined thereto on one side thereof, a movable diaphragm within said chamber deining operating and vacuum chambers on opposite sides thereof, a vacuum source joined to said housing and conducted therethrough to said vacuum and operating chambers, air inlet ports in said housing, a power rod secured to said diaphragm and slidably disposed through said housing, said rod having a partial longitudinal passage terminating in said operating chamber and within said housing, a movable diaphragm provided within said housing and carrying a normally seated air valve, a hydraulic cylinder joined to said housing upon its other side, and a movable valve piston therein normally in spaced relation to said valve diaphragm to permit vacuum communication to said operating chamber, but adapted on movement thereof to close olf said vacuum communication, and on further movement unseat said air valve to establish air communication to said operating chamber.

5. The combination, an air and vacuum valve housing, a vacuum source joined thereto, air inlet ports in said housing, a pressure ,differential motor including a movable member dening a vacuum chamber and an operating chamber, a longitudinally reciprocal power rod actuated thereby and slidably disposed through said valve housing, said rod having a, partial longitudinal passage terminating in said operating chamber and within said housing, and movable means in said housing for providing air and vacuum communication to said motor.

6. The combination, an air and vacuum valve housing, a vacuum source joined thereto, air inlet ports in said housing, a pressure differential motor including a movable member defining a vacuum chamber and an operating chamber, a longitudinally reciprocal power rod actuated thereby and slidably disposed through said valve housing said rod having a partial longitudinal passage terminating in said operating chamber and within said housing, movable means in said housing for providing air and vacuum communication to said motor, and manually actuated means engageable with said movable means.

7. The combination, an air and vacuum valve housing, a vacuum source joined thereto, air inlet ports in said housing, a pressure differential motorincluding a movable member defining a vacuum chamber and an operating chamber, a longitudinally reciprocal power rod actuated thereby and slidably disposed through said valve housing said rod having a partial longitudinal passage terminating in said operating chamber and within said housing, and movable diaphragm means in said housing for providing air and vacuum communication to said motor.

8. The combination, an air and vacuum valve housing, a vacuum source joined thereto, air inlet ports in said housing, a pressure differential motor including a movable member defining a vacuum chamber and an operating chamber, a longitudinally reciprocal power rod actuated thereby and slidably disposed through said valve housing said rod having a partial longitudinal passage terminating in said operating chamber and within said housing, a movable diaphragm in said housing for regulating air and vacuum communication to said motor, an air valve seat in said housing, an air valve joined to said dia- 15 16` phragm, and manually actuated vacuum controll Number Name Date means engageable with said diaphragm, and 2,308,460 Stelzer Jan. 12, 1943 adapted' to elect movement thereof. 2,336,374 Steiger Dec. 7, 1943 GORDON R. ELLIOTT. 2,372,014 Rockwell Mar. 30, 1945 5 2,388,220 Rockwell Oct. 30, 1945 REFERENCES CITED 2,393.3.'324y Pant Jan. 22, 1946 The following references are of record in the 2,398,252 Rockwell APT- 9: 1946 le of this patent: FOREIGN PATENTS' UNITED 10 Number Country Date 1,548,232 Westbrook Aug 4, 1925 290,980 Great Britain Dec. 20, 1928 1,766,481 Bragg June 24, 1930 

